There exists an abundance of insect pest species that can infect or infest a wide variety of environments and host organisms. Insect pests include a variety of species from the insect Orders Hemiptera (true bugs), Coleoptera (beetles), Siphonaptera (fleas), Dichyoptera (cockroaches and mantids), Lepidoptera (moths and butterflies), Orthoptera (e.g. grasshoppers) and Diptera (true flies). Pest infestation can lead to significant damage. Insect pests that infest plant species are particularly problematic in agriculture as they can cause serious damage to crops and significantly reduce plant yields. A wide variety of different types of plant are susceptible to pest infestation including commercial crops such as rice, cotton, soybean, potato and corn.
Traditionally, infestation with insect pests has been prevented or controlled through the use of chemical pesticides. However, these chemicals are not always suitable for use in the treatment of crops as they can be toxic to other species and can cause significant environmental damage. Over more recent decades, researchers have developed more environmentally-friendly methods of controlling pest infestation. For example, microorganisms such as Bacillus thuringiensis bacteria that naturally express proteins toxic to insect pests have been used. Scientists have also isolated the genes encoding these insecticidal proteins and used them to generate transgenic crops resistant to insect pests e.g. corn and cotton plants genetically engineered to produce proteins of the Cry family.
Although bacterial toxins have been highly successful in controlling certain types of pest, they are not effective against all pest species. Researchers have therefore looked for other more targeted approaches to pest control and in particular to RNA interference or ‘gene silencing’ as a means to control pests at the genetic level.
RNA interference or ‘RNAi’ is a process whereby the expression of genes in the context of a cell or whole organism is down-regulated in a sequence-specific manner. RNAi is now a well-established technique in the art for inhibiting or down-regulating gene expression in a wide variety of organisms including pest organisms such as fungi, nematodes and insects. Furthermore, previous studies have shown that down-regulation of target genes in insect pest species can be used as a means to control pest infestation.
WO2007/074405 describes methods of inhibiting expression of target genes in invertebrate pests including Colorado potato beetle. WO2005/110068 describes methods of inhibiting expression of target genes in invertebrate pests including in particular Western corn rootworm as a means to control insect infestation. Furthermore, WO2009/091864 describes compositions and methods for the suppression of target genes from insect pest species including pests from the Lygus genus.
Although the use of RNAi for down-regulating gene expression in pest species is known in the art, the success of this technique for use as a pest control measure depends on selection of the most appropriate target genes, namely those wherein loss of function results in significant disruption of an essential biological process and/or death of the organism. The present invention is thus directed towards the down-regulation of particular target genes in insect pests as a means to achieve more effective prevention and/or control of insect pest infestation, particularly of plants.